feat: implement dynamic tool discovery via MCP notifications/tools/li…

[makanilani]

Pull Request

Title

feat: implement dynamic tool discovery via MCP notifications/tools/list_changed

URL

main...makanilani:goose:dynamic-tool-discovery

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Description

Summary

When MCP servers send notifications/tools/list_changed (e.g., Google Colab servers that register tools dynamically), Goose now invalidates its tool cache so the next agent turn sees the updated tool set.

Problem

Currently, Goose calls tools/list once during initialization and never checks for updates. The rmcp crate's ClientHandler trait provides on_tool_list_changed() with a default no-op implementation, and GooseClient does not override it — so the notification is silently dropped.

Changes

• Add ToolCacheInvalidator trait in mcp_client.rs
• Implement ToolCacheInvalidator for ExtensionManager
• Add tool_cache_invalidator field to GooseClient
• Implement on_tool_list_changed handler in GooseClient's ClientHandler impl (overrides rmcp's default no-op)
• Thread invalidator reference through all MCP client construction paths (StreamableHttp, Stdio, Builtin, InlinePython)

Architecture

MCP Server → notifications/tools/list_changed
  → GooseClient::on_tool_list_changed() (new)
    → ExtensionManager::invalidate_tools_cache_and_bump_version() (existing)
      → Agent reads fresh tools on next turn via get_prefixed_tools()

Files Changed

• Cargo.lock
• crates/goose/src/agents/mcp_client.rs
• crates/goose/src/agents/extension_manager.rs

Testing

Observed Google colab mcp server works after the change.

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Co-authored-by: Qwen-Coder qwen-coder@alibabacloud.com

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Break strong reference cycle when wiring tool invalidator

Passing Arc::clone(self) as the ToolCacheInvalidator creates a retain cycle: ExtensionManager holds each client in extensions, and each McpClient now holds a GooseClient that keeps this strong Arc<ExtensionManager> in tool_cache_invalidator (mcp_client.rs). When a session/agent is removed, this cycle prevents ExtensionManager and its clients from dropping, so child MCP processes and temp resources can leak across sessions. Please switch this back-reference to a Weak-based invalidator (or an explicit teardown path) so session cleanup can actually release clients.

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[DOsinga]

Thanks for the PR — handling notifications/tools/list_changed is something we do need.

A few things to address before we can move forward:

1. Reference cycle (Codex P1): The Arc::clone(self) as Arc<dyn ToolCacheInvalidator> creates a strong reference cycle (ExtensionManager → extensions → McpClient → GooseClient → tool_cache_invalidator → ExtensionManager). Please use Arc::downgrade with a Weak-based wrapper instead.

2. Tests: The two tests added are testing implementation details (that a field is stored, that a mock works) rather than the actual feature. test_on_tool_list_changed_calls_invalidator never actually calls on_tool_list_changed — it just calls invalidate_tools() directly on the stored field. Please either write tests that exercise the real notification path or remove the trivial tests.

3. DCO: The commit is missing the required Signed-off-by line — CI is failing on the DCO check. See the check output for instructions on how to fix this.

4. Cargo.lock: There's a spurious goose-sdk version bump in the lockfile that's unrelated to this change — please revert that.

/cc @alexhancock